There is known, as a configuration of connecting nodes of an optical communication network, star connection using a relatively small number of optical fibers required for the connection. As a method for realizing a full-mesh connection by means of this star connection, there is known, for example, a method using an array waveguide grating described in Background Art of Patent Literature 1 described later. FIG. 35 shows a structure of the array waveguide grating described in the Patent Literature 1. FIG. 36 shows a logical connection structure of the array waveguide grating described in the Patent Literature 1. FIG. 37 shows a table of wavelength correspondence of input-output port pairs of the array waveguide grating.
As shown in FIG. 37, the array waveguide grating outputs different wavelengths input from the same input port from different output ports, respectively. Furthermore, the array waveguide grating outputs the same wavelength input from different input ports from different output ports, respectively. Accordingly, full-mesh connection among nodes can be realized by arranging multiplexers-demultiplexers or the like multiplexing and demultiplexing wavelengths λ1 to λ5 in the respective nodes.
Meanwhile, it is effective to apply, for example, wavelength multiplexing using a plurality of wavelengths so as to enlarge a transmission band. However, as shown in FIG. 37, the number of types of wavelengths used for the inter-node connection is one according to the above-stated method. Due to this, it is difficult to enlarge the transmission band among the nodes. It is also difficult to deal with a communication congestion that possibly occurs among the nodes, a communication failure and the like.
To solve this problem, the Patent Literature 1 proposes a configuration for connecting arbitrary input/output ports of the array waveguide grating as shown in FIG. 38. Further, as a method for solving similar problems, Patent Literature 2, to be described later, discloses a method for switching routes using an optical switch as disclosed in, for example. Moreover, Patent Literature 3, to be described later, discloses a network that can connect arbitrary nodes to one another by a combination of a tunable wavelength light source and an array waveguide grating.